Very good for close up at f1,8, very soft corners and some CA, better at f2,8. Central resolution and acutance are excellent from f4 to f8, corners are good from f5,6 to f11. CA and distortion are low.Acutance is very good. Resolution is low at f1,8 and f2,8. Vignetting is important up to f2,8. AF is good.

This is a very good lens,its at 1.8 wide open already very sharp.ofcourse it has light falloff in the corners bud thats something every fast wideangle lens has.at 4.0 this problem has solfed.Ate F 5.6 itz RAZOR SHARP from edge to edge. Forget all the other revieuws,I have one myself, i now what i am talking aboud.Other revieuw websites always debunk Sigma because they are sponserd by Canon and Nikon too do so and too promote their own products.I defenily advies too buy this lens.,itz very ...

This lens is great for landscapes, very sharp, even good in the corners where I use it--on a tripod at f5.6-8. the build is not superior but adequate. The performance is as good as much more expensive lenses.

This lens is a mixed bag for sure. For what it is its pretty impressive. On Full Frame its pretty much one of if not "the" fastest ultra wide angle lens. I would not really want to use this on crop sensor cameras, its not worth the trade offs. This lens has the old manual focus clutch, switch system, which I have never liked. Further the ring is so big its really easy to pick it up and change from MF to AF. At 1.8 the edges aren't great, but the center is. But hey it can do 1.8 what else can? ...